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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_PREEMPT_H
#define __ASM_PREEMPT_H
#include <asm/rmwcc.h>
#include <asm/percpu.h>
#include <linux/thread_info.h>
DECLARE_PER_CPU(int, __preempt_count);
/* We use the MSB mostly because its available */
#define PREEMPT_NEED_RESCHED 0x80000000
/*
* We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
* that a decrement hitting 0 means we can and should reschedule.
*/
#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
/*
* We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
* that think a non-zero value indicates we cannot preempt.
*/
static __always_inline int preempt_count(void)
{
return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
}
static __always_inline void preempt_count_set(int pc)
{
int old, new;
do {
old = raw_cpu_read_4(__preempt_count);
new = (old & PREEMPT_NEED_RESCHED) |
(pc & ~PREEMPT_NEED_RESCHED);
} while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old);
}
/*
* must be macros to avoid header recursion hell
*/
#define init_task_preempt_count(p) do { } while (0)
#define init_idle_preempt_count(p, cpu) do { \
per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
} while (0)
/*
* We fold the NEED_RESCHED bit into the preempt count such that
* preempt_enable() can decrement and test for needing to reschedule with a
* single instruction.
*
* We invert the actual bit, so that when the decrement hits 0 we know we both
* need to resched (the bit is cleared) and can resched (no preempt count).
*/
static __always_inline void set_preempt_need_resched(void)
{
raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
}
static __always_inline void clear_preempt_need_resched(void)
{
raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
}
static __always_inline bool test_preempt_need_resched(void)
{
return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
}
/*
* The various preempt_count add/sub methods
*/
static __always_inline void __preempt_count_add(int val)
{
raw_cpu_add_4(__preempt_count, val);
}
static __always_inline void __preempt_count_sub(int val)
{
raw_cpu_add_4(__preempt_count, -val);
}
/*
* Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
* a decrement which hits zero means we have no preempt_count and should
* reschedule.
*/
static __always_inline bool ____preempt_count_dec_and_test(void)
{
return GEN_UNARY_RMWcc("decl", __preempt_count, e, __percpu_arg([var]));
}
static __always_inline bool __preempt_count_dec_and_test(void)
{
if (____preempt_count_dec_and_test())
return true;
#ifdef CONFIG_PREEMPT_LAZY
if (preempt_count())
return false;
if (current_thread_info()->preempt_lazy_count)
return false;
return test_thread_flag(TIF_NEED_RESCHED_LAZY);
#else
return false;
#endif
}
/*
* Returns true when we need to resched and can (barring IRQ state).
*/
static __always_inline bool should_resched(int preempt_offset)
{
#ifdef CONFIG_PREEMPT_LAZY
u32 tmp;
tmp = raw_cpu_read_4(__preempt_count);
if (tmp == preempt_offset)
return true;
/* preempt count == 0 ? */
tmp &= ~PREEMPT_NEED_RESCHED;
if (tmp != preempt_offset)
return false;
if (current_thread_info()->preempt_lazy_count)
return false;
return test_thread_flag(TIF_NEED_RESCHED_LAZY);
#else
return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
#endif
}
#ifdef CONFIG_PREEMPT
extern asmlinkage void ___preempt_schedule(void);
# define __preempt_schedule() \
asm volatile ("call ___preempt_schedule" : ASM_CALL_CONSTRAINT)
extern asmlinkage void preempt_schedule(void);
extern asmlinkage void ___preempt_schedule_notrace(void);
# define __preempt_schedule_notrace() \
asm volatile ("call ___preempt_schedule_notrace" : ASM_CALL_CONSTRAINT)
extern asmlinkage void preempt_schedule_notrace(void);
#endif
#endif /* __ASM_PREEMPT_H */
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